The invention generally relates to medical forceps systems comprising forceps which can be dismantled. More specifically, the invention relates to dismantlable forceps having a grip, a shaft, a force transmission element and a tool at the distal end.
A dismantlable medical forceps system known under the brand name CLICKline® is marketed by Karl Storz GmbH & Co. KG and is described, for example, in the company catalogue Storz Karl Storz-Endoskope, Laparoscopy Volume, 5th edition, 2005, pages 72 et seq.
Medical forceps are used in open surgery or in endoscopic surgery, for example for cutting, gripping, coagulating, etc., of tissue in the human or animal body.
Medical forceps generally have a grip with at least one movable grip part, an elongate shaft connected to the grip, at least one movable tool, for example jaw part, at the distal end of the shaft, and a force transmission element, usually in the form of a pull and push rod, which forms a force-fit connection between the at least one movable tool and the at least one movable grip part of the grip. By moving the at least one movable grip part, the force thereby generated is transmitted from the force trans-mission element to the at least one movable tool, in order to move the latter.
In order to permit better cleaning, medical forceps of this kind are designed such that they can be dismantled. The dismantlable forceps can usually be dismantled into the structural groups of grip, shaft and force transmission element, the at least one tool being connected as a structural unit to the force transmission element and being designated also as a working insert of the forceps.
The dismantlable nature of medical forceps not only increases the ease with which the forceps can be cleaned, it also increases the variability of function of such forceps, since different grips can be combined with different shafts and/or work inserts.
The known forceps system comprises, on the one hand, several different grips and, on the other hand, a plurality of different shafts and work inserts. Thus, the grips can differ in terms of the maximum force that can be generated, for example by providing grips whose at least one movable grip part can generate a high force because of a high lever action, while other grips are made smaller and generate a correspondingly lower force. A higher force is necessary, for example, for cutting or punching bone tissue, whereas a smaller handgrip is better suited for fine dissecting of softer tissue, because it permits better control of the force exerted by the physician's hand.
The force transmission elements too can differ in terms of the maximum force that can be transmitted by them. The maximum force that can be transmitted by the respective force transmission element is limited by the thickness of the force trans-mission element and of its connection element for connection to the movable grip part. For cutting bone tissue, a high force must be transmitted from the force trans-mission element to the at least one tool at the distal end, such that a force transmission element for these purposes has to be designed with a certain thickness, for example with a diameter of 3 mm. This also entails a correspondingly larger external diameter of the outer shaft through which the force transmission element extends between the grip and the at least one tool.
By contrast, in spatially confined surgery, for example in the ENT sector, very slender outer shafts of small diameter are needed, such that the force transmission element also has to be made relatively thin, for example with a diameter of approximately 1 mm.
To achieve the best possible compatibility, it is desirable that force transmission elements designed to transmit different maximum forces can be connected to one and the same grip, so as to minimize as far as possible the number of grips that have to be provided.
However, the known dismantlable forceps system mentioned above does not allow force transmission elements with different diameters to be received in one grip. Rather, the connection elements of the force transmission elements and of the coupling device of the grip or grips are of uniform design, with the result that each force transmission element can be connected only to one and the same grip. This leads, however, to the technical problems explained below, particularly when force transmission elements having very different thicknesses and, consequently, load-bearing capacities are intended to be combined in one forceps system.
When the work insert is preassembled, the force transmission element is pushed from the distal direction through the outer shaft. The connection element at the proximal end of the force transmission element is designed, for example, in the shape of a ball and also has to be able to pass through the outer shaft until it emerges from the proximal end of the outer shaft. If the force transmission element is designed to transmit a high force, the connection element also has to be designed with a suitable thickness in order to ensure that the connection between the force trans-mission element and the grip is able to withstand high forces. To allow the connection element of relatively large dimension to pass through the outer shaft, the outer shaft must have a relatively large diameter. Such a forceps system then has the disadvantage that, when the grip is connected to a thinner force transmission element, the outer shaft still has to have the same large diameter as in the case where a more strongly dimensioned force transmission element is connected to the grip, so as to ensure the compatibility between different force transmission elements and the same grip. Otherwise, a second grip with another coupling device would have to be made available, which is not consistent, however, with the objective of greater compatibility and undesirably increases the number of different grips.
Conversely, if the connection between the force transmission element and the grip is designed for the force transmission element permitting a low maximum force transmission, such that the connection element at the proximal end of the force transmission element can be made smaller, then, although the size of the outer shaft can be variable and in particular made thin, the maximum force that can be transmitted nevertheless remains limited to that of the smallest or weakest force transmission element. This means that when tools that require great force, for example bone punches, are used with a grip of suitably large dimension, breakage of the force transmission element in the area of the connection element cannot be ruled out when the grip is actuated with substantial manual force.
In this case, therefore, the physician operating the forceps has to carefully control the manual force exerted, so as to avoid breaking the force transmission element.
The known medical forceps system therefore has the disadvantage that the connection elements of the existing force transmission elements are intended for only one thickness, which results either in undesirably large external diameters of the outer shafts or in the risk of breakage of the force transmission element.